1. Field of the Invention
The invention concerns an exhaust gas purification device of the type wherein a reforming reactor is provided for extraction of hydrogen from fuel and the hydrogen is supplied to an exhaust gas stream of an internal combustion engine upstream of the exhaust gas catalytic converter, and a process for operating the device.
2. Description of the Related Art
From U.S. Pat. No. 5,412,946 A1 an exhaust gas purification device for a vehicle is known, in which hydrogen is introduced into the exhaust gas stream in order to reduce nitrous oxide in the exhaust gas catalytic converter. The hydrogen is obtained by reforming, for examplexe2x80x94from the co-introduced fuel (hydrocarbons), and is introduced together with oxygen and water into the reforming unit. Therein the content of the supplied hydrogen is adjusted depending upon the amount of NOxxe2x80x94 in the exhaust gas stream. Water for reforming is provided by a water tank and is vaporized prior to the reforming process, while oxygen is drawn in in the form of ambient air and is supplied to the reforming device.
The invention is concerned with the task of providing an exhaust gas purification device with which a simplified system becomes possible.
This task is solved by an exhaust gas purification device in a vehicle, wherein a reforming reactor is provided for extraction of hydrogen from fuel and the hydrogen is supplied to an exhaust gas stream of an internal combustion engine upstream of the exhaust gas catalytic converter, wherein the reforming reactor includes a supply device for oxygen and/or water, wherein the reforming reactor is connected with a side branch of the exhaust gas conduit and wherein oxygen and water for reforming are supplied in the form of an exhaust gas partial stream via the side branch, and a process for operating the device.
In accordance with the invention, for reforming, the water and oxygen that are employed are exclusively from the exhaust gas stream. The requirement for supplemental media tanks and corresponding control devices can thus be dispensed with.
The advantage is comprised therein, that H2 and CO can be obtained in simple manner in the vehicle as the reducing agents for the NOx-removal in the conventional exhaust gas post-treatment. The feed material for the inventive process originates from the fuel tank accessible in the vehicle and the internal combustion exhaust gas. There is no need to carry supplemental materials on board the vehicle. No tanks and measuring devices are required for the supplemental materials.
Preferably an electrical heating means is employed only during the heating phase; later, the partial exhaust gas stream supplied to the reformer can be regeneratively pre-heated by the hot product gas stream. The autothermic process requires, in the stationary case, no electrical heating from outside. Thus electrical energy can be saved.
The employment of a catalyst on a carrier structure makes possible minimal pressure losses, so that the pressure in the side branch is comparable with that in the exhaust gas conduit. The amount of catalyst itself is lower and exhibits a better efficiency than in the case of the conventionally employed bulk catalyst. The amount of catalyst which is dispensed with corresponds to an amount which need not be heated.
It will be readily understood that the above mentioned features and the following discussed features need not be employed only in the respective discussed combinations, but rather can be employed also in other combinations or by themselves, without leaving the framework of the present invention.